The three dimensional ultrastructure and physiological function of the human crystalline lens are directly related to its transparency and ts ability to change contour during accommodation. During the aging process, the lens gradually loses its clarity and elasticity, thus reducing its functional capacity. By using slit-lamp tomography, the precise location and size of the lens opacity can be determined and, upon extraction, can be studied using scanning and transmission electron microscopy as well as biochemical analysis. The proposed study is designed to analyze changes in human and animal lenses which occur during normal aging and during disease processes and, to relate these data to clinical observations. The techniques in our laboratory have been well established by our work on the rat and normal human lens. With the continued co-operation of the New Jersey Eye Bank and the Departments of Ophthalmology, Obstetrics and Pathology, normal and abnormal lenses are readily obtained through our established Fetal and Adult Human Lens Retrieval System. Thus, in human and animal systems, the ultrastructural architecture of the lens, its capsule, epithelium and zonular apparatus will be determined and correlated with the biochemical data of Dr. Fu and coworkers (Department of Biochemistry). Our findings will give additional information and new insight into the aging process of the lens and its loss of functional integrity.